1. Field of the Invention
The present invention relates to an image information displaying system and hologram displaying apparatus, capable of being installed in a showroom and so forth, for presenting image information including moving and still images.
2. Description of the Related Art
Image information displaying systems are widely used to present image information including moving and still images to passersby and viewers in front of showrooms. These systems are composed of a screen and a unit for supplying image information to the screen.
A typical image information displaying system employs a videotape, an optical disk, or slides to store image information, a video deck, an LD player, or a projector to reproduce the image information, and a CRT or a liquid-crystal panel to display the reproduced image information.
Poorly presented image information hardly attracts the attention of passersby, and therefore, hardly realizes advertising and eye-catching effects.
Image information to be displayed must be adjusted so that it can be recognized easily by people. If image information is poorly adjusted and is hardly recognizable, it will not appeal to, or attract the attention of, people.
Image information must be adjusted according to ambient conditions around the location where the image information displaying system is installed. It is very difficult to adjust image information beforehand. In particular, when the system is installed outdoors or facing the outdoors, the values of parameters used to adjust image information vary from hour to hour and are dependent on weather and seasonal conditions.
Usually, the system is continuously operated to always display image information. The system, therefore, consumes a large amount of power and energy, has high running costs, and has a short service life.
A conventional image information displaying system comprising a screen and a means for supplying image information to the screen finds application as a means for presenting image information, as still pictures or a moving picture, from a showroom or the like to passersby and other viewers in general.
Specifically, the image information recorded in the videotape, the optical disk, slides or the like is reproduced and presented using a displaying system such as a CRT or a liquid crystal panel connected to various reproduction or playback apparatuses including a video deck, an LD player and a projector.
Consider the case in which an image information displaying system is used for presenting information to chain store outlets or branch offices located over wide areas.
In such a case, for the image information displaying system of each outlet or branch office to be operated practically, it is necessary to teach the operating know how to each outlet and branch office and to train the staff therein. This poses no problem if the image information displaying systems are installed within a small area or in a small number or the workers are limited in number. In the case where the image information systems are installed over a wide area, in many units or must be operated by many workers, however, the presentation of information requires the troublesome and expensive work of training the workers, distributing operating manuals, etc.
No available image information displaying system places sufficient emphasis on reduced costs for management and practical operation (education and training as examples) of each of a multiplicity of systems installed over a wide area.
In the case where the image information displaying system is used for displaying a commercial for a commodity, for example, the mere presentation of image information on the image displaying system can hardly attract the attention or interest of passersby or viewers, making effective advertisement difficult. In other words, the eye-catching effect is small.
The operation of an image information displaying system, therefore, requires an appropriate adjustment of the image information to make it easily visible to passersby and viewers and to attract their attention even more. The adjustment for presenting more visible image information may include brightness adjustment, color drift correction, determination of appropriate hue or adjustment of the position at which the image is displayed.
As long as the image information is difficult to recognize due to insufficient adjustment, the image information is less appealing to passersby and viewers and a good eye-catching effect is often difficult to produce.
To cope with the above-mentioned problems and to improve the eye-catching effect, a method has been conceived to install a means for adjusting the image information with each image information displaying system. The adjusting means, however, makes the image information displaying system more expensive. In addition, the maintenance and inspection as well as the operation of the adjusting means often increases the system cost.
Also, since the image information displaying system is kept in operation for presenting image information, the reproduction or playback unit and the display unit thereof are also kept in operation. The power consumed by these units is so large as to pose problems from the viewpoints of energy saving and running cost. Further, the protracted operation time of the reproduction unit and the display unit shortens the service life thereof.
New display systems employing plasma display units, thin liquid-crystal display units, and projection television units are being developed to present still and moving images to passersby in front of showrooms.
To enhance an advertising effect, these systems must be made larger. The larger systems, however, frequently provide an oppressive feeling to viewers. This limits their possible locations, usability, and design flexibility.
To solve the problem and realize a high advertising effect, a display system employing a hologram screen has been proposed.
The hologram screen, as will be explained later in detail, consists of a transparent base and a thin-film hologram element attached thereto. The hologram element has interference fringes. When light containing image information is emitted onto the interference fringes, the light forms a real image, which is diffracted by the hologram element. Viewers see the real image reproduced on the hologram element.
The hologram element is transparent, and the hologram screen does not require a power source or a driver. The hologram screen, therefore, needs only a small installation space and the designing freedom thereof is good.
One problem of the hologram screen is that it has a limited viewing angle within which people can see images on the hologram screen. Accordingly, the hologram screen must be carefully installed so that viewers can correctly see images thereon.
To achieve correct positioning of the hologram screen, many experiments have been made. For example, a mirror method surrounds a light diffuser with mirrors to produce-object beams that irradiate a photosensitive material from different directions. The object beams and a reference beam record intricate interference fringes on the photosensitive material. The photosensitive material is used as a hologram element of a hologram screen.
Even the hologram screen made by the mirror method has a limited viewing angle. Namely, the hologram element of the mirror method involves parts where no light diffuser is recorded, and therefore, images on the hologram screen are partly invisible depending on viewer""s positions. At some position, images on the hologram screen provide low brightness, different colors, or poor quality for viewers.
In this way, it is very difficult to sufficiently expand the viewing angle of a hologram screen.
In view of the first viewpoint of the prior art, a first object of the present invention is to provide an image information displaying system capable of providing excellent eye-catching effects, reduced energy consumption and running costs, and an extended service life.
In order to accomplish the object, a first aspect of the present invention provides an image information displaying system having a transparent support, a hologram screen attached to the support, a projector for projecting image information onto the screen, a sensor for sensing ambient conditions within a viewing angle of the hologram screen, and a controller for controlling the projector according to signals from the sensor.
The hologram screen may be of a transmission type or of a reflection type.
To improve an eye-catching effect, preferably, the hologram screen may be transparent so that viewers may see a background and exhibits behind the screen.
The transparent hologram screen and support may achieve an effect of suddenly displaying image information in a vacant space to greatly attract the attention of people.
The transparent hologram screen does not disturb the view of other people, thereby improving the degree of freedom in designing and installing the system.
The transparent support may be a show window made of glass or resin, a front or rear window of a mobile body such as a car, a vessel, an airplane, or a train, a window panel of an office or a shop, or a wall made of glass or plastics of a guest room, or any other space.
The projector may be a slide projector, an overhead projector (OHP), or any device for projecting moving and still images.
The projector may receive image information from an external supply unit, which may be a player of videotapes and optical disks, or information processing equipment such as a personal computer connected to the Internet.
The projector emits a beam of image information onto the hologram screen, which diffracts and diffuses the beam into a conical area. Only within the conical area is the image information visible.
More precisely, each beam of image information from the projector forms a conical area on the hologram screen, and a viewer can see an image only in an overlap of such conical areas. These conical areas define a viewing angle of the hologram screen. The viewing angle will be explained later in detail.
A plurality of image information displaying systems may be installed and linked to one another. In this case, each system may have a sensor (embodiment A2), or the systems may share a single sensor.
The operation of the first aspect of the present invention will be described in the following.
The sensor senses ambient conditions in the viewing angle of the hologram screen, and the controller controls the projector according to signals from the sensor.
This system is capable of automatically starting, optimizing, and stopping image information provided by the projector according to ambient conditions detected in the viewing angle of the hologram screen.
For example, if the illuminance in the viewing angle is high, the system increases the brightness of image information, or changes the image information itself to another having a higher brightness, so that viewers may easily recognize the images.
If voices are sensed in the viewing angle, the system determines that there are people in the viewing angle and activates the projector to present image information to the people.
In this way, the present invention automatically changes the conditions and kinds of image information and starts and stops image information according to ambient conditions that vary from hour to hour.
The system provides eye-catching image information to strongly attract people""s attention.
The projector may be automatically started and stopped according to situations, to shorten an actual operation time of the projector, thereby reducing power consumption and running costs.
Shortening the operation time of the projector may extend the service life thereof.
In this way, the system of the present invention reduces energy consumption and running costs and extends the service life.
A second aspect of the present invention defines the viewing angle of the hologram screen in an area where brightness is K0/2 or over (K0 being a brightness value at a front center point of the hologram screen).
Brightness within the viewing angle of the hologram screen is high and, therefore, viewers in the viewing angle may clearly recognize images on the hologram screen. Accordingly, images within the viewing angle achieve a high eye-catching effect.
In an area where brightness is below K0/2, viewers may recognize image information but may hardly grasp the contents thereof. In this case, the eye-catching effect of the image information is low. The brightness of the hologram screen is highest at the center thereof.
The details of K0 and the viewing angle of a hologram screen will be explained later.
A third aspect of the present invention employs, as the sensor, an illuminance sensor so that the image information displaying system may present optimum image information in the viewing angle of the hologram screen.
A fourth aspect of the present invention provides the image information displaying system with a speaker for providing audio information. In this case, the sensor is a volume sensor.
This arrangement provides audio information as well as image information, thereby providing an improved eye-catching effect.
The volume sensor senses a sound volume in the viewing angle of the hologram screen and feedback-controls the speaker, to optimize audio information as well as image information according to ambient conditions. If not needed, the speaker may be stopped to reduce running costs and prolong the service life.
A fifth aspect of the present invention uses the sensor to detect the presence of people in the viewing angle of the hologram screen.
If people enter the viewing angle of the hologram screen, the fifth aspect activates the projector to project image information, or switches displayed image information to another.
If no image information is displayed, the hologram screen is inconspicuous to passersby. Accordingly, the fifth aspect may provide a high eye-catching effect by suddenly displaying image information in a vacant space where the hologram screen is installed.
The fifth aspect is capable of activating the projector only when people are present in the viewing angle of the hologram screen. This shortens an operation time of the projector, reduces power consumption and running costs, and prolongs the service life of the system.
The sensor may be an infrared sensor, a voice sensor, a vibration sensor, a weight sensor arranged on the floor, etc. A single sensor, a plurality of sensors, or a various types of sensors may be used in combination.
The sensor may sense not only people entering the viewing angle of the hologram screen but also people going out of the viewing angle. If the sensor senses that people enter the viewing angle, the controller starts the projector to project image information, and if the sensor senses that people exit the viewing angle, the controller stops the projector.
The arrangement of the fifth aspect secures the effect of the present invention.
A sixth aspect of the present invention installs the image information displaying system in a mobile body.
If the hologram screen is transparent, it does not bother the sight of people. In this case, the system does not block a driver of the mobile body from seeing the outside through the hologram screen. Accordingly, the system can be installed in a mobile body.
The system installed in a mobile body is used to display driver assisting information such as navigation information, or alarm information to the outside of the mobile body.
If the mobile body is a car, the system may display image information for passengers in the rear seat of the car.
A seventh aspect of the present invention arranges the image information displaying system between two seats of a mobile body.
This arrangement prevents the hologram screen from being exposed to the sun, thereby extending the service life thereof.
More precisely, this arrangement prevents discoloration and performance deterioration due to ultraviolet rays and heat from the sun.
An eighth aspect of the present invention makes the hologram screen of the image information displaying system retractable when it is not used.
This arrangement effectively uses a limited space in a mobile body. When the hologram screen is retracted, it is protected from being discolored or deteriorated due to ultraviolet rays and heat from the sun. This arrangement also makes the installation of the system into a mobile body easier.
The retractable hologram screen may be realized by winding, folding, or detaching of the screen.
The hologram screen may be arranged on a sunroof. In this case, a viewer sets himself or herself on a fully reclined seat to see image information.
The hologram screen may be integrated with or embedded in a seat of a mobile body (FIG. 14).
A ninth aspect of the present invention employs, as the sensor of the image information displaying system, a vibration sensor. The vibration sensor senses the vibration of a mobile body in which the system is installed. In response to signals from the vibration sensor, the controller of the system corrects a blur of image information on the hologram screen due to the vibration of the mobile body (FIG. 15).
A tenth aspect of the present invention employs the vibration sensor to suppress the vibration of the projector of the system against the vibration of the mobile body in which the system is installed (FIG. 16).
When the mobile body vibrates, the projector may provide blurred images. This problem is serious when the mobile body is large such as a bus or a truck because the vibration thereof is also large.
The tenth aspect uses the vibration sensor to detect vibration, electrically corrects image information according to signals from the vibration sensor, and projects the corrected image information from the projector onto the hologram screen, thereby correcting a blur of images on the screen.
The tenth aspect may have a mechanism for suppressing the vibration of the projector. The mechanism is driven in response to signals from the vibration sensor, to correct a blur of images on the hologram screen.
The system of the tenth aspect is capable of displaying blur-free images in the mobile body.
The mechanism for suppressing the vibration of the projector may be a damper or a piezoelectric actuator.
An eleventh aspect of the present invention connects image information displaying systems to a central control unit through a communication circuit and controls the systems by the central control unit.
The central control unit centrally controls and manages the systems, to save manpower.
The communication circuit may be a public or private voice circuit (telephone circuit), a moving image circuit of, for example, a cable television service using optical cables, or a radio circuit such as a communication satellite digital circuit. Any wire or wireless communication circuit can be used for the eleventh aspect. The Internet can also be used.
Image information to be displayed may be held at the image information displaying systems or at the central control unit. In the latter case, the central control unit can centrally manage image information, to reduce management costs.
For example, each image information displaying system is installed in each branch office, and the central control unit in the head office, which distributes new product information simultaneously to the branch offices so that the branch offices may release an announcement of the new product at the same time. This saves the labor of sending materials related to the new product to the branch offices beforehand.
In another example, each image information displaying system is installed in each chain store, and the central control unit in the head office. This provides the same effect as the above example. In addition, updating commodity information is made only in the central control unit. This eliminates each chain store""s labor of updating the commodity information.
If the central control unit must hold image information, it is preferable to employ a high-speed communication circuit such as a wide-band private circuit to distribute the image information to the branch offices or chain stores.
A twelfth aspect of the present invention makes the central control unit receive signals from the sensor of each system through a communication circuit and controls the projector of the system in question according to the signals to project image information onto the hologram screen of the system.
This arrangement secures the effect of the present invention.
A thirteenth aspect of the present invention records a diffuser on the hologram screen of the image information displaying system.
This aspect provides an effect of displaying full-color images on the hologram screen.
In view of the above-mentioned problems in the second viewpoint of the prior art, a second object of the invention is to provide an inexpensive image information displaying system which has a low maintenance/inspection cost, a low running cost and a long service life.
In order to achieve the second object described above, according to a 14th aspect of the invention, there is provided an image information displaying system comprising a transparent support, a hologram screen attached to the transparent support, and a radiation unit for irradiating the hologram screen with image information, the image information displaying system being controlled by a central control unit connected thereto through a communication line.
The central control unit can be configured as a mainframe computer or various work stations or the like, for example. For improving the effect of the invention further, each central control unit is desirably connected with a great number of image information displaying systems.
Various communication lines are available for use including the audio communication lines such as the telephone network and leased lines, optical fiber cables for distribution of image sequences used on the cable TV or the like, radio channels such as the CS digital line using an earth satellite, or various other wire and wireless channels. A computer network such as the Internet can also be used.
A transmission-type hologram screen can be used as the above-mentioned hologram screen. A hologram screen of a reflection type is another candidate.
A transparent hologram screen is desirable for assuring an improved eye-catching effect. This makes possible a configuration in which viewers can see commodities exhibited and the background behind the hologram screen through the hologram screen.
Also, for its ability to present image information suddenly in an apparently vacant space (although a transparent support and a hologram are actually installed), the hologram can attract the attention and interest of viewers considerably.
Further, the image information displaying system, which can be configured to not interfere the viewing field of viewers, can be installed with a higher freedom.
The transparent support includes window glass made of various types of glass or plastics, the rear and front glass of various mobile bodies (such as automobiles, seagoing vessels, airplanes and electric trams), the window glass used in branch offices and retail outlets, and the glass window panes and transparent walls arranged around a guest room or the like.
The radiation unit, on the other hand, includes a slide projector, an OHP (overhead projector), a liquid crystal projector, a motion picture projector and various other devices capable of radiating still images and image sequences.
The image information can be supplied to the radiation unit also from an external source. External information sources include reproduction or playback units such as videotape and optical disk players and information processing systems such as personal computers connected to the internet. Also, image information can be distributed from a central control unit.
The operation and effects of the 14th aspect of the invention will be explained.
The image information displaying system according to this aspect of the invention is so configured as to be controlled by a central control unit connected thereto through a communication line.
The central control unit makes possible the collective management and practical operation of the image information displaying systems, thereby reducing the cost for management and practical operation which otherwise would be required on the part of the image information displaying system. The staff and labor cost can thus be reduced.
Since the job of management and practical operation of the image information displaying system can be left to the central control unit, the construction of each image information displaying system is simplified for a correspondingly reduced cost thereof. In other words, the image information displaying system can be constructed in so simplified a fashion as to have only the functions of displaying images and accepting the control from the central control unit.
The simplicity of the image information displaying system reduces the system cost on the one hand and the maintenance cost for repair and inspection as well as the running cost at the same time. The simple construction is also a factor in reducing the number of system faults.
Further, the various adjustments of the parts of the image information displaying system which can be accomplished from the central control unit facilitates the system operation. The labor of educating and training the workers can thus be saved. Also, the simplicity of the system configuration can produce an image information displaying system easy to handle even by unskilled workers.
An example of the mechanism for management and operation is a diagnosis mechanism for discovering a fault and deterioration at an early time. Provision of the diagnosis mechanism in the central control unit lengthens the service life of the system while at the same time preventing the image information displaying system from being complicated in structure and increased in cost.
It is also possible to start and stop the operation of the image information displaying system at a preset time. The system can be suspended from operation or put into continuous operation or otherwise controlled by the central control unit. Since the image information displaying system can thus be operated only when required and can be controlled in fine detail, the system life is lengthened and the running cost thereof is reduced.
In addition, emergency and newspaper information, as well as the original image information to be displayed, can be selected as desired by the management thereof.
The hologram screen irradiated with the image information displays the image by diffraction and scattering the radiated beam containing the image information. The hologram which has no power supply and no driving unit contributes to reduction in running cost and saves energy for the image information displaying system according to the invention.
As described later, the hologram screen requires some correction and adjustment for displaying a clear-cut, normal image having a strong impact on, and giving a vivid impression to, viewers.
The image information displaying system according to this invention, which can be adjusted and corrected by the central control unit, eliminates the need of the various troublesome jobs of adjustment and correction on the part of the image information displaying system, thus reducing the management cost and labor in general.
The data for image information radiated can be incorporated in either the image information displaying system or the central control unit. In the latter case, the image information can be centrally controlled by the central control unit for a reduced management cost.
Assume, for example, that a party for unveiling a new product is held in all branch offices at the same time. The image information displaying system according to the invention is installed in each branch office and the central control unit in the head office from which the information on the new product can be distributed to the branch offices in various areas. This saves the trouble of distributing the information on the new product to various areas in advance.
Another example application is to install the image information displaying system at each outlet of a chain store or the like and the central control unit at the headquarters. This has the same effect as the preceding case. Further, the information on commodities can be updated simply by updating the image information incorporated in the central control unit.
For locating the image information in the central control unit, a high-speed communication line (wide-area leased line, for example) is desirably used.
The 14th aspect of the invention described above can thus provide an inexpensive image information displaying system with low running, maintenance and inspection costs and a long service life.
A 15th aspect of the invention is desirably configured in such a way that the central control unit alone corrects the image-information, or in such a way that the central control unit or a relay interposed between the central control unit and the image information displaying system corrects the image information.
The provision of the relay permits part of the processing in the central control unit to be transferred to the relay. The processing can thus be distributed between the central control unit and the relay, thereby making it possible to improve the stability and speed of the processing of the whole network including the central control unit and the image information displaying system.
In addition, a local area network can be formed with the relay as a base. Thus finely detailed control meeting local requirements is made possible.
Also, the following general properties of the hologram screen are known. Specifically, the scattered beam emitted from the hologram screen often has a peak in a specified wavelength range, even when the incident beam is white, often with the result that the tone of the image reproduced on the hologram screen is different from that of the radiated beam.
For this reason, image color adjustment and color correction are crucial in using the hologram screen.
The image information displaying systems distributed to various points are adjusted by individual workers. Due to the difference in color sense from one person to another, however, it is very difficult to adjust and correct the color of the images displayed on all the image information displaying systems to the same state.
The collective control using the central control unit as in the 15th aspect of the invention, however, can maintain the same state of the image information displayed on a multiplicity of systems distributed over a wide area. At the same time, the labor of the workers is reduced. This labor saving effect can reduce the cost and trouble of the whole management.
The fact that the image information can be corrected by the central control unit or the relay makes it possible to display a correct image normally free of a color drift between the radiated beam and the displayed image.
Also, the elimination of the need of correction and adjustment on the part of the image information displaying system can save the equipment for image information correction which otherwise would be required in each image information displaying system. The cost of the image information displaying system can thus be reduced. Further, since the cost for repair and inspection and the running cost of the correction unit is not required, the system cost can accordingly be reduced.
Furthermore, in displaying a commercial of a commodity as image information, for example, the sponsor of the commercial who emphasizes the image of the commodity may request the faithful reproduction of fine color texture of the image information.
With the image information displaying system according to the 15th aspect, the image information can be collectively corrected at the central control unit and therefore such a request can be readily met.
It is also possible to incorporate the image information in the central control unit, and after correction, distribute it among the image information displaying systems for display. The image information stored in each image information displaying system can also be corrected individually.
According to a 16th aspect of the invention, the above-mentioned correction is preferably that of a trapezoidal distortion.
In order to prevent the radiated beam from directly entering the eyes of the viewer, the radiation unit is generally installed at an angle to the hologram screen. The radiation unit, therefore, is often located at a position diagonally above or below the hologram screen.
Locating the radiation unit at such a position may cause a trapezoidal distortion of the image on display as shown in FIG. 33a. 
According to this aspect of the invention, as shown in FIG. 33b, the trapezoidal distortion of the image information is reversely corrected by the central control unit in advance. Therefore, as shown in FIG. 33c, the image information displaying system can display a normal image.
As in the 15th aspect, the image information displaying system is not required to correct the trapezoidal distortion. Therefore, the trapezoidal distortion correction unit can be eliminated from the image information displaying system, and the cost of the image information displaying system can be reduced.
Other details are similar to those of the 15th aspect.
Also, as the 16th aspect of the invention, the correction described above is desirably at least one of the processes including the color adjustment, color correction, image position adjustment, image brightness adjustment and the image contrast adjustment.
As a result, a clear-cut image having a strong impact on viewers can be displayed.
According to a 17th aspect of the invention, the image information displaying system includes means for supplying audio information, and the central control unit or the relay is preferably configured to correct the audio information.
The provision of the means for supplying audio information leads to an image information displaying system having a superior eye-catching effect which can present both image information and audio information.
As in the 15th aspect, the correction of audio information is not required on the part of the image information displaying system, and therefore the audio information correction unit can be eliminated from the image information displaying system. The cost of the image information displaying system can thus be reduced.
Other details are similar to those of the 15th aspect.
The processing for correcting the audio information includes the automatic starting and automatic stopping of the system, adjustment of sound volume or sound quality, selection and switching of audio information, etc.
The means for supplying audio information is a speaker, for example.
According to an 18th aspect of the invention, the image information displaying system preferably comprises a sensor for detecting the ambient conditions within the viewing angle of the hologram screen and a radiation control unit configured to control the radiation unit based on the signal from the sensor.
As described above, in the case where the image information displaying system is used for presenting a commercial of a commodity, the mere image information appearing on the image information displaying system fails to attract the attention and interest of passersby or viewers, thereby making effective advertisement and publicity difficult. In other words, the eye-catching effect is low.
When using an image information displaying system, therefore, it is necessary to adjust the image information to a most visible form for passersby and viewers in such a manner as to attract their maximum attention. As long as the system is not sufficiently adjusted and the image information remains difficult to recognize, the image information is less appealing to passersby and viewers and can rarely produce a good eye-catching effect. The adjustment for this purpose may include adjusting the brightness for making the image easy to see, correcting the color drift, selecting an appropriate hue and adjusting the position at which the image is displayed.
The effective adjustment of the image information depends on the environment in which the image information displaying system is installed. Therefore, it has thus far been difficult to preset adjustment values for the image information displaying system. Especially in outdoor applications or applications at a location facing the outdoor environment, the optimum adjustment values for the image information system undergo a constant change with time, weather conditions and the season of the year.
With the image information displaying system according to the 18th aspect of the invention, the condition and type of image information can be changed or the presentation of the image information can be started or stopped automatically in accordance with the various ambient conditions undergoing a constant change within the viewing angle.
In the case where the ambient illuminance within the viewing angle is high, for example, the brightness of the image information is increased or the image information is changed to the one of higher brightness or otherwise image information easily visible to viewers can be supplied.
When the voice of a person is sensed within the viewing angle, for example, the presence of a viewer within the viewing angle is assumed and the radiation unit is activated to supply the image information to the particular viewer.
As a result, the image information can be supplied with such a high eye-catching effect as to attract the attention of the viewer sufficiently.
In the image information displaying system according to the 18th aspect, the radiation unit can be configured to operate automatically as required and therefore the substantial operation time of the radiation unit can be shortened. The power consumption of the radiation unit can thus be saved for a lower running cost.
Also, the shorter operating time of the radiation unit can lengthen the service life thereof.
As described above, according to the 18th aspect of the invention, an image information displaying system is provided which has a high eye-catching effect, is low in running cost and has a long service life.
Further, a plurality of image information displaying systems according to the invention can be used in coordination with each other through a central control unit. In such a case, the image information displaying systems each can be provided with a sensor (embodiment B2) or can share a sensor.
According to a 19th aspect of the invention, the viewing angle is desirably located in an area having a brightness of at least K0/4 (K0 represents the brightness value at the front center of the hologram screen).
The brightness of the hologram screen as viewed from within the above-mentioned viewing angle is so high that the viewer standing within the viewing angle can recognize the image information on the hologram screen as a bright and clear-cut image. The image information displaying system according to this aspect, therefore, can present image information having a good eye-catching effect.
In the brightness range of less than K0/4, the viewer can recognize the image information but may find it difficult to comprehend the contents of the image information. A reduced eye-catching effect is the probable result.
The hologram screen has such a feature that the image information issued from the radiation unit and impinged on the hologram screen can be observed on the hologram screen only from within a conical space formed by diffraction and diffusion of the image information (radiated beam).
The image information on the hologram screen, therefore, is visible only in an area where conical spaces formed by the image information (radiated beam) impinged on various parts of the hologram screen are overlapped. This area constitutes a viewing angle, which will be described later in detail.
The brightness of the hologram screen, on the other hand, assumes the highest value at the center thereof.
According to a 19th aspect of the invention, the sensor described above is preferably an illuminance sensor. This makes it possible to realize an image information displaying system capable of presenting optimum image information corresponding to the brightness within the viewing angle.
According to a 20th aspect of the invention, the sensor is desirably a volume sensor.
The sound volume within the viewing angle can be sensed by the volume sensor. Thus, the sound volume information with the sound volume most suitable for the prevailing ambient conditions can be supplied in addition to the image information. If the sound volume information is not required, a device such as the speaker for supplying audio information can be deactivated for reducing the running cost and lengthening the service life of the system.
According to a 21st aspect of the invention, the sensor is desirably configured to sense the entry of the viewer into the viewing angle.
Thus, an image information displaying system is realized in which, when a viewer enters the viewing angle of the hologram screen, the radiation unit is activated to radiate the image information or the image information is switched.
The hologram screen is so inconspicuous that it is not easily recognized by the viewer until image information is displayed thereon. For this reason, the invention makes it possible to present a situation in which image information suddenly presents itself in a thus far empty space and thus a good eye-catching effect can be produced.
Also, as described above, according to this invention, the radiation unit can be activated as soon as the viewer enters the viewing angle. The operation time of the radiation unit can thus be shortened for a reduced power consumption and running cost. The service life of the system can also be lengthened.
The above-mentioned sensor can include an infrared sensor, an audio sensor, a vibration sensor or a weight sensor installed on the floor. These sensors can be used individually or a plurality of sensors or sensor types can be used in combination.
The above-mentioned sensor desirably detects both the entry into and exit from the viewing angle of the viewer. In response to the signal from this sensor, the radiation control unit desirably causes the image information to be radiated from the radiation unit when the viewer enters the viewing angle and deactivates the radiation unit when the viewer leaves the viewing angle.
As a result, the effect of the invention can be secured more positively.
According to a 22nd aspect of the invention, the image information displaying system is desirably mounted on a mobile body.
The use of a transparent hologram can produce a transparent image information displaying system which does not interfere with the field of view. Such an image information displaying system has the effect of providing a lesser chance of preventing both the driving, and the observation of the outside, of the mobile body. The image information displaying system according to the invention thus is suitably installed on a mobile body.
The image information displaying system installed on a mobile body can be used for displaying driving-support information like the car navigation system or a warning to other mobile bodies.
In the case where the mobile body is an automotive vehicle, the image information displaying system is usable as a display unit for rear-seat passengers, for example.
According to a 23rd aspect of the invention, the image information displaying system is desirably installed between at least two seats in a mobile body (FIG. 29).
As a result, the hologram screen is prevented from being directly exposed to sunlight and thus early degeneration of the hologram screen is prevented.
Specifically, it is possible to prevent discoloring or performance deterioration due to the ultraviolet light and the heat of direct sunlight.
According to a 24th aspect of the invention, the hologram screen is desirably retractable into an appropriate means when not in use.
This makes possible the effective utilization of the limited internal space of the mobile body. Also, the retraction of the hologram screen when not in use can further prevent the discoloring, the performance reduction and deterioration thereof which otherwise might be caused by the ultraviolet light and the solar heat. Further, other work in the mobile body may be facilitated.
Specifically, the hologram screen is desirably provided as a roll-up, folding or detachable type.
The hologram screen can also be arranged on the sunroof. In this case, the hologram screen can be configured in the form of full flat sheet on which the image information can be observed.
Another possible configuration is integrating the hologram screen with or embedding it in the front passenger seat or the head rest (FIG. 30).
According to a 25th aspect of the invention, the sensor is a vibration sensor, and the radiation control unit is desirably configured to correct the blur of the radiated image information caused by the vibration of the mobile body based on the signal from the vibration sensor.
According to a 26th aspect of the invention, the sensor is a vibration sensor and the radiation control unit is desirably so configured as to suppress the vibrations of the radiation unit due to the vibrations of the mobile body based on the signal from the vibration sensor.
In the case of installing various display units on a mobile body, the problem of image blurring due to vibrations of the mobile body is encountered especially by a display unit which projects the image information by a radiation unit. This problem is especially serious for large-sized vehicles such as buses and trucks.
According to this invention, a blurred image is corrected in such a manner that vibrations are detected by a vibration sensor, and the data making up the image information is electrically corrected based on the detected signal and radiated from the radiation unit.
Alternatively, a mechanism for suppressing the vibrations of the radiation unit can be provided and driven based on the signal from the vibration sensor to correct the image blurs.
These means can produce an image information displaying system by which image information can be viewed with little blurring on a mobile body.
Means for absorbing the vibrations of the radiation unit include a damper and a piezo-actuator.
According to a 27th aspect of the invention, preferably, the central control unit or the relay receives the signal from the sensor through the communication line, and based on the same signal, controls the radiation control unit.
In the image information displaying system according to the 27th aspect, as in the embodiment B1 described later, the ambient condition within the viewing angle of the hologram screen is detected by a sensor, and the resulting signal representing the ambient condition is applied from the sensor to the central control unit or the relay. The central control unit or the relay, upon receipt of this signal from the sensor, can control the radiation control unit in keeping with the ambient condition within the viewing angle.
As a consequence, the central control unit or the relay can perform various control operations such as activating and deactivating the radiation unit, switching the image information radiated from the radiation unit or correcting or adjusting the image information in accordance with the ambient condition within the viewing angle.
In other words, according to this embodiment, the image information displaying system can perform the control operation taking the ambient condition of the image information displaying system into consideration, substantially free of manual operation. Also, an image information displaying system high in energy-saving ability is provided.
According to a 28th aspect of the invention, a diffuser is preferably recorded in the hologram screen.
This makes it possible to produce an image information displaying system capable of projecting a full-color image and to further improve the eye-catching effect.
The diffuser described above can be a light diffuser such as ground glass.
In view of the above-mentioned problems described in the third viewpoint of the prior art, a third object of the present invention is to provide a hologram displaying system capable of displaying a superior image and having a high eye-catching effect.
In order to achieve the third object described above, according to a 29th aspect of the invention, there is provided a hologram displaying system comprising a hologram screen, and a projector for projecting an image beam on the hologram screen, wherein the lower end of the hologram screen is located at the distance of 80 to 180 cm from the floor level.
The hologram screen will be explained.
The hologram screen can be classified into a hologram of transmission type for transmitting an image beam therethrough and a hologram screen of reflection type for reflecting an image beam. The present invention can use either type of the screen.
As shown in FIGS. 51(a) to 51(f), 52(a) to 52(f), 53(a) to 53(f) described later, various shapes of screen can be used. Further, although the hologram screen can be used with the image beam projected over the entire surface thereof to display an image as described with reference to FIG. 54 later, the image beam can be projected on part of the hologram screen using the zoom function of the image projector to display the image.
The hologram screen of a transmission type is the one with the image projector arranged at the back of the screen. The image beam projected from the image projector is focused and forms a real image on the hologram screen. A person can recognize the image by the diffracted light scattered and transmitted from the real image.
The hologram screen of reflection type, on the other hand, is the one using the image projector arranged on the front side of the screen. The image beam projected from the image projector is focused and forms a real image on the hologram screen. A person can recognize the image by the diffracted beam scattered and reflected from the real image.
In a method of fabricating the hologram screen, a beam constituting an object beam diffused through a light diffuser such as ground glass and a non-diffused beam constituting a reference beam are projected on a photosensitive material to form interference fringes. An example of the fabrication method will be explained below.
In fabricating a hologram screen of a transmission type, as shown in FIG. 48, a coherent beam 34 radiated from a laser beam source 51 is changed in light path by a mirror 511, and then split into two beams 341, 342 by a half mirror 512.
After the beam 341 is scattered by a lens 516, transmitted through a light diffuser 52, and the resulting diffused beam is projected as an object beam 36 on a photosensitive material 50.
The other beam 342 split by the half mirror 512 is changed in light path by mirrors 513, 514, scattered by a lens 515, and projected on the photosensitive material 50 as a reference beam 35. The reference beam 35 and the object beam 36 form interference fringes on the photosensitive material 50. In FIG. 48, the corrugation shows a model of the diffused beam.
In fabricating a hologram screen of a reflection type, on the other hand, as shown in FIG. 49, the reference beam 35 and the object beam 36 are projected from opposite sides of the photosensitive material 50 to form interference fringes.
A PET film is attached to the surfaces of the photosensitive material 50 obtained by the process mentioned above to form protective films, thus making up a hologram screen.
Various devices are usable as an image projector. They include a slide projector, an OHP (overhead projector), a projector, a movie projector or other devices that can project an image beam of still pictures and image sequences.
It is also possible to supply an image to the image projector from external devices such as a videotape, an optical disk, a personal computer or other reproduction units. The reproduction unit can, of course, be built into the projector. Further, the image can be supplied from an external source using the telephone line, an earth satellite or the like channel.
In the case where the height of the hologram screen is less than 80 cm, the line of eyesight of the viewer is liable to depart considerably from the viewing angle specific to the hologram element, often making it difficult for the viewer to observe the image of a superior quality. This also applies in the case where the height of the hologram screen is more than 180 cm, in which case the image is sometimes difficult to see for the same reason.
The xe2x80x9csuperior imagexe2x80x9d, is defined as an image having a small color difference with and having substantially the same brightness, contrast and luminance as the image beam projected from the projector.
Also, the hologram displaying system according to this invention can be installed either indoor or outdoor. For the hologram displaying system installed outdoor, the xe2x80x9cfloor levelxe2x80x9d indicates the ground level.
As shown in FIG. 55 described later, the floor level is defined as the floor level 311 on which a viewer 8 of the hologram displaying system stands.
Also, as shown in FIGS. 51(a) to 51(f), 52(a) to 52(f) and 53(a) to 53(f) described later, the hologram screen can assume various shapes. The lower end of the hologram screen is also shown in the drawings.
The hologram screen can be configured either in flat form or in a curved form having a radius of curvature.
The hologram screen can have a very thin portion. Any portion where a image visible to the viewer cannot be displayed, however, fails to play the role of the hologram screen of the image displaying system according to the invention. Therefore, such a very thin portion cannot be considered as a lower end. The lower end of the hologram screen can be determined taking the above fact into consideration.
A hologram screen according to a 29th aspect of the invention uses interference fringes. The hue and brightness of the image on display, therefore, are varied depending on the angle at which the image is viewed. In other words, the hologram screen has some portions easy to view and other portions difficult to view. The portion where a superior image is clearly visible is called the viewing angle.
The viewing angle will be specifically described with reference to FIGS. 34 and 35.
The hologram screen has the feature that the image is invisible from other than a conical space formed by diffraction and diffusion of the image beam impingeing on the hologram screen from the projector.
Therefore, the image is visible only in an area where individual conical spaces formed as the image beam impingeing on various portions of the hologram screen are overlapped one over the other. This area constitutes a viewing angle.
In FIG. 34, the image beam 125 projected from an image projector 12 fans out and reaches a hologram screen 11. The image beam 125 that has impinged on the upper end 112 of the hologram screen 11 is scattered and transmitted while fanning out. Also, the image beam 125 that has hit the lower end 111 of the hologram screen 11 also fans out.
Similarly in FIG. 35, the image beam 125 that has impinged on the left end 113 and the image beam 125 that has impinged on the right end 114 of the hologram screen 11 also fan out.
The foregoing description refers to the plan views of FIGS. 34 and 35, and therefore the diffusion of the image beam 125 is expressed as xe2x80x9cfan outxe2x80x9d. Actually, however, the image beam assumes a conical shape as it diffuses into the space.
The image displayed on the hologram is known to become difficult to view when the brightness of the image decreases to less than one half of the central brightness. The central brightness is defined as the brightness of the image at the center of the hologram screen.
Consequently, the viewing angle 89 on the hologram screen 11 represents the sectorial area in the diagrams of FIGS. 34 and 35.
Now, the operation and effects of the 29th aspect of the invention will be explained.
In the hologram displaying system according to this invention, the hologram screen is installed under the above-mentioned conditions. The viewing angle of the hologram screen, therefore, is included in the line of sight of the viewer.
As described above, the interior of the viewing angle is an area where a superior image is visible. Therefore, the hologram displaying system according to this invention can display a superior image.
In this respect, the hologram displaying system according to the 29th aspect of the invention can display an image highly appealing to the viewer. In addition, the hologram screen is easily configured to be transparent, and therefore, the viewer feels that an image is projected in an otherwise empty space.
Consequently, the hologram displaying system according to the 29th aspect of the invention has the effect of attracting the attention of persons, i.e. has a superior eye-catching effect.
As will be seen from the foregoing description, according to the 29th aspect of the invention, there is provided a hologram displaying system capable of displaying a superior image and having a good eye-catching effect.
The photosensitive material used for fabricating the hologram element is generally composed of photo-polymer. The portion of the photo-polymer to which the laser beam is applied is crosslinked and formed with interference fringes.
Also, for a superior image to be displayed on the hologram screen described above, the interference fringes desirably remain in the same state as immediately after fabrication (initial state).
The interference fringes, however, are liable to be deteriorated by heat.
Consider, for example, the case in which a hologram element is attached to a transparent support like window glass to make up a hologram screen. The difference in thermal expansion coefficient exists between the hologram element and the transparent support. When the hologram element and the transparent support are heated, therefore, a thermal stress occurs between them. This thermal stress sometimes causes the distortion of the photo-polymer making up the hologram element.
The distortion of the interference fringes causes a distorted diffraction of the image beam, with the result that the image reproduced on the hologram screen is likely to develop a distortion.
Heat sources considered to cause this problem include the heat of the image beam itself, the hot air produced from the cooling fan or the like installed on the projector, the direct sunlight in high-temperature seasons such as the summer, and the heat reflected from the ground surface.
With the hologram displaying system according to the 29th aspect of the invention, the hologram screen is installed under the above-mentioned conditions.
The hologram screen thus is installed some distance off the floor and has a spatial margin with the floor surface. As a result, the hologram screen is prevented from being heated by the heat which otherwise might stay around the hologram screen.
The hologram screen, if it has a height of less than 80 cm, is liable to be exposed to the heat radiated back from the ground surface. Also, the proximity to the floor surface often causes the heat to remain due to the inefficient heat radiation.
In the case where the hologram screen has a height of more than 180 cm, on the other hand, the image is not easily visible.
Especially a hologram screen used by being attached to the glass is desirably held between biaxial oriented PET films or the like having a thermal expansion coefficient similar to that of glass (3 to 10xc3x9710xe2x88x926 cm/xc2x0 C.) in order to alleviate the thermal effect efficiently.
With the hologram displaying system according to the 29th aspect of the invention, the projector can be installed either above or under the hologram screen (embodiments C1, C2). It is also possible to arrange the hologram displaying system at a position diagonally above or below the hologram screen.
In the case where the projector is arranged below the hologram screen and the image beam is projected from under the hologram screen, the hologram screen should be located as high as possible. In the case where the projector is arranged above the hologram displaying system, in contrast, the hologram screen is desirably located as low as possible. In this way, the zero-order beam from the projector (the image beam projected from the projector) is prevented from entering into the eyes of the viewer.
According to a 30th aspect of the invention, there is provided a hologram displaying system comprising a hologram screen and a projector for projecting the image beam on the hologram screen, wherein the center height of the hologram screen is 110 to 210 cm from the floor level.
Also, with the hologram displaying system according to the 30th aspect of the invention, as described above, the viewing angle of the hologram screen comes just in the range of the line of sight of the viewer and therefore a superior image can be displayed in the range of the viewer""s field of view.
In this respect, the invention can display an image highly appealing to the viewer. In other words, the system has a good eye-catching effect.
As described above, according to the 30th aspect of the invention, there is provided a hologram displaying system capable of displaying a superior image and having a high eye-catching effect.
In the case where the center height is less than 110 cm, the line of the viewer""s sight is liable to depart from the viewing angle, and therefore the image hue is deteriorated making the image not easily visible. In the case where the height is more than 210 cm, in contrast, the hologram screen is installed at a correspondingly high position and the image is also liable to be not easily visible.
The reference floor level for measurement of the center height in this example is also represented by the floor surface 311 on which the viewer 8 stands, as shown in FIG. 55.
Also, the fact that the hologram screen is installed under the above-mentioned conditions prevents the heat from remaining around the hologram screen.
In the case where the center height is less than 110 cm, the hologram screen is exposed to the heat radiated back from the floor surface and the heat is liable to stay around the hologram screen.
According to a 31st aspect of the invention, there is provided a hologram displaying system comprising a hologram screen and a projector for projecting the image beam on the hologram screen, wherein the angle of projection of the projector to the hologram screen is 20 to 50 degrees.
With the hologram displaying system according to the 31st aspect in which the projection angle is set within the range mentioned above, the viewing angle of the hologram screen is just within the range of the viewer""s line of sight. A superior image can thus be displayed within the range of the viewer""s line of sight.
In this respect, the system according to the invention can display an image highly appealing to the viewer, i.e. it has a good eye-catching effect.
In the case where the projection angle is less than 20 degrees the zero-order beam from the projector intrudes the viewer""s eyes and is liable to make normal observation of the image impossible.
In the case where the projection angle exceeds 50 degrees, in contrast, the trapezoidal distortion of the image projected on the hologram screen increases to such an extent that a normal image becomes difficult to observe.
As shown in FIG. 34 described later, the projector is sometimes installed at a position diagonally above or below as well as just above or below the hologram screen for projecting the image beam.
It is shown in FIG. 43 that the projection angle of a indicates the state in which the projector is installed on the circumference of a circle constituting the bottom of a cone assumed to have an apex at the center of the hologram screen.
Specifically, as shown in FIG. 43, assume that image projectors are installed at a position t1 above the hologram, at a position t2 below the hologram screen, at a position t3 diagonally above the hologram screen and at a position t4 diagonally below the hologram screen. The projection angle of all the projectors is the same and xcex1.
As in a 32nd aspect of the invention, the hologram displaying system desirably comprises a trapezoidal distortion correction mechanism.
There is thus provided a hologram displaying system capable of displaying a correct image free of a trapezoidal distortion on the hologram screen and permitting the viewer to observe a correct image.
The trapezoidal distortion correction mechanism may include a trapezoidal distortion correction circuit capable of correcting the image electrically or a correction device for correcting the image optically using a lens.
According to a 33rd aspect of the invention, the diagonal length of the hologram screen is desirably not less than 30 inches and the projection distance of the image beam is desirably not less than 90 cm.
This permits the projector to be installed in a limited space while at the same time securing an image size of not less than 30 inches which is sufficiently large to produce an eye-catching effect. Also, substantially all the projectors sold on the market can be used.
The diagonal length indicates the length of the diagonal line of a substantially rectangular hologram screen. In the case where the diagonal length is less than 30 inches, the eye-catching effect is liable to be insufficient.
The upper limit of the diagonal length, though not specifically defined, is a value that can secure the distance from the floor level described in each of the claims.
The projection distance is defined as the distance between the surface of the hologram screen and the image beam projection unit of the projector (such as the lens of the liquid crystal projector).
In the case where the projection distance of the image beam is shorter than 90 cm, the diagonal length of the image probably is less than 30 inches. At the same time, the projector projects the image of itself on the hologram screen and undesirably becomes visible to the viewer.
The upper limit of the projection distance is desirably set to 350 cm. In the case where this upper limit is exceeded, the installation space increases to such an extent that the projector cannot be easily suspended from a low ceiling. Even in the case where the projector is installed on the floor, a sufficient space may not be secured. Further, even when the image is focused by the zoom function of the projector, the image often overflows the hologram screen.
According to a 34th aspect of the invention, the relation y=ax+b (where x is the diagonal length in inches, y is the projection distance in cm, and a, b are coefficients depending on the projector involved) is desirably satisfied between the diagonal length of the hologram screen and the projection distance.
As a result, the size of the hologram screen can be matched with the performance of the projector, thereby saving the installation space.
For Projector TH-L392J of Matsushita Electric Industrial Co., for example, a=4.6 and b=xe2x88x9223.7.
Generally, the coefficient a assumes a value of xe2x88x9220 to xe2x88x9230.
As shown in FIG. 39 described later, in the case where a plurality of hologram screens are arranged side by side and used as a single large screen, the diagonal length of the combined large screen is employed as the diagonal length L of the hologram screen under consideration.
According to a 35th aspect of the invention, the hologram screen is desirably installed in an environment where the contrast (defined as (brightness of white image screen+background brightness+external beam brightness)/(brightness of black image screen+background brightness+external beam brightness)) is not less than 1.5. This secures an image appearance having a sufficient eye-catching effect.
In the case where the contrast is less than 1.5, the image appearance is so inferior that a sufficient eye-catching effect may not be secured. A more desirable upper limit of the contrast is 300. For a contrast higher than this value, the image becomes too bright and often difficult to view.
The brightness of white image screen is the brightness of the normal white screen input on a personal computer, and the brightness of black image screen is the brightness of the black screen input on a personal computer. Also, the background brightness is the brightness of an object behind the hologram screen, and the external beam brightness is the brightness of an object projected on the hologram screen.
For realizing the above-mentioned environment, a configuration as described below is desirably provided for the hologram displaying system.
For example, the projector is desirably configured in such a manner that a sensor for detecting the brightness around the hologram screen is operatively interlocked with means for adjusting the image brightness and the image size.
Also, as in the embodiment C7 described later, a polarizing film or an antireflection film is desirably incorporated in the hologram screen to reduce the background brightness and the external beam brightness for an improved contrast.
The hologram displaying system according to this invention is desirably installed in such a position that the hologram screen is not exposed to sunlight directly. This arrangement can exclude the adverse effect of heat while at the same time improving the contrast of the environment of the hologram screen to not less than 1.5 as described above.
If an antireflection film, a polarizing film or the like is mounted on the hologram screen as such a protective means like in the embodiment C7 described later, a normal image can be observed even at a very bright place under direct sunlight.
Also, a sunshade, a peak or a blind can be provided for protection from direct sunlight.
According to a 36th aspect of the invention, the hologram screen is chamfered at the corners thereof, or the section of the hologram is tapered.
As a result, the hologram screen is not easily removed.
As shown in the embodiment C1 described later, the hologram screen installed on the window glass or the like is prevented from coming off at the time of cleaning the window.
The wording xe2x80x9cthe corners are chamferedxe2x80x9d is indicative of the fact that what is called at least a corner R is formed. The corners of the hologram screen are thus formed as shown in FIGS. 37(a), 37(d) described later, for example.
The wording xe2x80x9cthe section is taperedxe2x80x9d means configuring a hologram screen into the state as shown in FIGS. 37(c), 37(d) described later, for example.
According to a 37th aspect of the invention, the hologram screen is desirably installed by covering with water (stretch).
This allows for a sufficient time before being dried, during which the position of the hologram screen can be finely adjusted taking advantage of the slidability of water.
Adhesives usable for the above-mentioned stretch include acrylic ester copolymer, acrylic styrene copolymer, polyvinyl alcohol, polyvinyl butyral or the like, aqueous micromole, aqueous emulsion or the like, and an organic binder for plastic which becomes transparent when dried.
According to a 38th aspect of the invention, the projector is desirably fixed at an inclination angle of 20 to 50 degrees to the horizontal ceiling surface by a fixing jig.
As a result, the eyes of the viewer are protected from the zero-order beam of the image projector and the viewer can normally observe the image.
In the case where this angle is less than 20 degrees, the zero-order beam is liable to intrude the viewer""s eyes. For the inclination angle of more than 50 degrees, on the other hand, the image is often distorted excessively or an out-of-focus condition may develop.
The inclination angle of the projector to the horizontal ceiling surface will be explained.
Consider a straight line perpendicular to the surface on which the hologram screen is installed. In the case where this straight line is parallel to the ceiling surface (FIG. 34), the ceiling constitutes the horizontal ceiling surface. The angle that the ceiling forms with the projector is the inclination angle.
In the case where the straight line perpendicular to the surface on which the hologram screen is installed is not parallel to the surface of the ceiling (FIG. 56), on the other hand, the plane containing the particular straight line constitutes the horizontal ceiling surface. The angle that this horizontal ceiling surface forms with the projector constitutes the inclination angle.
The surface on which the hologram screen is installed is regarded as the plane containing the surface of the hologram screen in the case where the hologram screen is flat.
According to the 29th to 38th aspects of the invention, the hologram displaying system can also comprise various sensors which produces signals for controlling the operation of the projector. Thus, a system is realized which is automatically activated whenever required. The various sensors referred to above include those for detecting the brightness, weight, rain, humidity, temperature, odor, sunlight, etc.
On the other hand, a plurality of hologram screens can be combined side by side to construct a large-sized hologram screen. In this case, the image beam corrected in accordance with the properties of each hologram screen is projected, and thus an integrated image free of the sense of incompatibility as a whole can be observed.
The correction referred to above includes the adjustment of the hue, brightness, etc. of the image beam.